The present invention relates to a folder gluer. More specifically, the present invention relates to a folder gluer for conveying and folding up a cardboard sheet from a deployed state thereof.
Conventionally, as an apparatus for correcting a posture of a cardboard sheet to be conveyed, that is, an inclination of a cardboard sheet with respect to a conveying direction, a cardboard sheet posture correcting apparatus is known for, in a process line of a printing and/or a punching, correcting a posture of a sheet WS during a conveyance, so that a reference direction B of the cardboard sheet almost coincides with a sheet feed direction T, by a sheet rotating mechanism which rotates the sheet WS during a conveyance by a predetermined angle within a plane of the sheet, and then for conveying the cardboard sheet to a folder gluer, which is a next process, as disclosed in JP-11-105160-A.
Further, as an apparatus for correcting a posture of a cardboard sheet to be conveyed, in a carton former, a blank shear correcting apparatus is known for activating a shear correcting stopper by a detection signal via an automatic control system, when a blank is detected by a detecting sensor for a blank (a cardboard sheet), so as to correct the blank to a correct posture, and then for conveying the blank to a folder gluer for coving and/or gluing, which is a next process, as disclosed in JP-63-151443-A.
In addition, as an apparatus for correcting a posture of a cardboard sheet to be conveyed, in a folder gluer, an apparatus is known for correcting an inclination of a cardboard sheet by push-pressuring a rear end edge of the box body by a push pawl of the conveying belt with the pawls, so as to be pushed against a positioning member, and then pinching the box body from both the front and rear sides with the push pawl, as disclosed in JP-2006-035741-A.
In a folder gluer, a cardboard sheet is conveyed by two conveyer belts, in general. The inventors of the present invention have found by an experimental proof that, in the folder gluer, an inclination of a posture of the cardboard sheet from a normal posture is caused by a difference in the conveyance speeds of two conveyer belts. That is, when driving a frictional transmission belt (a flat belt) by a pulley with a frictional force, a speed difference is generated between two belts according to causes such as (1) a change in a surface texture by a variation with time of the belt surface which contacts the pulley differs between two belts (a change in a frictional transmission force between the pulley and the belt), (2) a variation in the conveyance speed by a speed-up of the conveyance speed of the conveyer belt, and (3) a load of the cardboard sheet to be conveyed, thereby the cardboard sheet is inclined with respect to the conveyance direction. Such inclination may result in a deformation of a box in the sheet folding-up step, and will causes a serious problem generating to be connected with a production deficiency. In particular, according to the aforementioned causes, the variation with time in which the speed variation of the conveyer belts varies slowly in time-wise will occur, and when, in the folder gluer, a great number of cardboard sheets would be conveyed continuously in a high speed, even though the folding-up could be made quite well in the first batch as shown in FIG. 8 (a), when the conveyance speed D would differ as shown in FIG. 8 (b), the problem could be caused, in which the deficiency would be generated in the last batch.
In the meantime, assuming that the cardboard sheet would be inclined with respect to the conveyance direction, the apparatuses disclosed in the aforementioned Japanese Patent Publications are provided with the rotating mechanism for correcting an inclination of a cardboard sheet (JP-11-105160-A), the blank shear correcting stopper (JP-63-151443-A), and the positioning member and the pushing pawl (JP-2000-0355741-A), and thus the apparatuses become a major structure, and costs much more. In addition, a displacement in an inclination of the cardboard sheet cannot be overcome by the aforementioned Japanese Patent Publications, and as a result, if the conveyance speed of the conveyer belt would be sped up as being desired in the industry, it could be difficult to correct the cardboard sheet to a normal posture accurately with the conventional art such as disclosed in the Japanese Patent Publications.
On the other hand, although the speed difference between two belts could be prevented to almost zero by arranging two conveying belts to be timing belts (synchronous belts), the timing belts are required to form the tooth part in order to obtain an accurate timing, the timing belts have a constraint condition such as a requirement of using a thick belt and an endless belt, and the timing belts are further expendable parts. Accordingly, the timing belts become extremely expensive.